In null steering apparatus for use with multiple antenna arrays, such as described in the following copending U.S. patent applications:
Ser. No. 744,008, now U.S. Pat. No. 4,079,379, filed Nov. 22, 1976, entitled "Null Steering Apparatus for a Multiple Antenna Array"; Ser. No. 744,009, now U.S. Pat. No. 4,079,380, filed Nov. 22, 1976, entitled "Null Steering Apparatus for a Multiple Antenna Array on an FM Receiver"; and Ser. No. 744,010, now U.S. Pat. No. 4,079,381, filed Nov. 22, 1976, entitled "Null Steering Apparatus for a Multiple Antenna Array on an AM Receiver", all assigned to the same assignee as the present application, a feedback circuit is utilized to null out signals introduced into the circuit by the antenna array and a reference signal is generated to subtract a desired signal from the feedback circuit to prevent the desired signal from being nulled out. The reference signal generated must be the same phase as the desired signal or there is a tendency for the feedback circuit to oscillate as the circuit attempts to adapt. This oscillation of the output signal is undesirable because it will cause the carrier frequency at the output to be at a different frequency than the received carrier frequency. Also, the oscillation tends to degrade the null depth when an undesirable signal is present.